Synonyms for Mitigation (same or very similar meaning)
WordNet sense 1 (a partial excuse to mitigate censure; an attempt to represent an offense as less serious than it appears by showing mitigating circumstances):
extenuationWordNet sense 2 (to act in such a way as to cause an offense to seem less serious):
palliationWordNet sense 3 (the action of lessening in severity or intensity):
moderationFrom the ODE community, based on WordNetadd/edit